This invention concerns clothes dryers and more particularly cycle controls for controlling the duration of dryer operation.
Clothes dryer controls generally include a manually settable timer dial which is rotated to a given position for proper drying of the clothes in a given cycle. The position to which it is rotated basically operates to set a run time timer, which in turn at least partially controls the duration of the operating cycle of the dryer. The timer setting may directly control the length of drying time as indicated by a scale bearing a legend corresponding to the number of minutes the cycle is set by rotation to a particular scale marking on the dial scale. Alternatively, in automatic drying cycles, the dial scale reference marking merely indicates the start point of the automatic drying cycle.
The automatic controls then cause the operation of the dryer until the moisture content of the load has reached a certain predetermined level as directly sensed or indirectly determined by sensing parameters such as exhaust air temperature.
After achieving the predetermined level, the dryer time begins to time out the remaining segment of the dryer operating cycle.
The user, by rotating the dial to the start of the operating cycle, sets into the timer the fixed time interval of dryer operation after the moisture level has been reduced to the predetermined level.
The length of this time interval has been set in at normal conditions; that is, average dryer operating conditions. The duration of this interval is selected to achieve proper final moisture levels for the average conditions.
It has been discovered that the length of time of dryer operation in order to achieve a certain optimum final moisture level varies with room ambient temperature. That is, as room ambient temperatures decrease, the length of time of dryer operation required in order to achieve proper drying is reduced, whereas with increasing ambient temperatures, the length of time increases.
Thus, particularly in the automatic control situation, the user sets in a particular setting for a given operational cycle and there will be a tendency for either underdrying or overdrying of the load, except under the design normal or average operating conditions. This may effect the performance and efficiency of the dryer since dryers may be operated in a wide variety of ambient conditions.
It is accordingly the object of the present invention to provide an arrangement for compensating for such variations in ambient temperatures in the dial setting for the dryer timer such that the effects on dryer run time are automatically compensated so as to optimize the dryer operating times.